Streptococcus uberis is an important mastitis-causing pathogen, responsible for a large proportion of both clinical and sub-clinical cases of mastitis in many parts of the world. The pathogen affects cattle, goats and sheep; however, infection of cattle is of primary importance due to its impact on the dairy industry, through welfare issues for affected animals, and also because of the significant financial impact on producers. As a species, S. uberis is highly-heterogenous; it is biochemically and physiologically ill-defined, and is serologically heterogenous (Hardie, 1986). Furthermore, there is evidence of genetic heterogeneity, driven predominantly through horizontal gene transfer (Coffey et al., 2006). Originally, DNA-DNA hybridization studies suggested the existence of two related S. uberis genotypes (designated types I and II) (Garvie & Bramley, Journal of Applied Microbiology, vol. 46, issue 2, pp. 295-304, 1979; Farrow et al., Syst. Appl. Microbiol., vol. 5, pp. 467-482, 1984), both associated with the bovine host and a cause of mastitis. Type II S. uberis was later re-classified as Streptococcus parauberis (Williams and Collins, 1990), which is also increasingly found as a cause of disease in fish; significantly, phylogenetic studies have since shown the two species to be related (Nho et al., 2011), and hence they are likely to share conserved portions of genome.
It is, in part, due to the heterogeneity of the S. uberis population that efforts to develop an effective vaccine have been unsuccessful. This is because S. uberis antigens which have been shown to have promise as vaccines have not always been found to be conserved amongst the broader population.
It is an object of the present invention to provide antigens which are conserved among strains of S. uberis and which may have use or be exploited, in vaccines and methods of diagnosis, detection and/or identification.